How to use the time zone converter
- Enter the date in YYYY-MM-DD format and the time in 24-hour HH:MM format.
- Select the source time zone from the From time zone dropdown.
- Select the destination time zone from the To time zone dropdown.
- Read the converted local time, date and UTC offset below the form.
How the time zone conversion works
The time zone converter first interprets the date and time you enter as a local moment in the source zone. It then finds the exact UTC instant that corresponds to that local moment, accounting for whether daylight saving time is active on that specific date. Finally it projects that UTC instant into the target zone to produce the local time there.
For example, converting 12:00 on 15 July 2025 from America/New_York to Europe/London: New York observes Eastern Daylight Time (UTC-4) in July, so 12:00 EDT equals 16:00 UTC. London observes British Summer Time (UTC+1) in July, so 16:00 UTC becomes 17:00 BST. The result is 17:00 on the same calendar day.
Common time zone offsets
The table below shows standard (winter) and daylight (summer) UTC offsets for several frequently used zones. Offsets change when DST starts or ends, which is why a proper time zone calculator must reference the full IANA database rather than a fixed offset.
| IANA Zone | Common Name | Standard Offset | DST Offset |
|---|---|---|---|
| America/New_York | Eastern Time | UTC-5 | UTC-4 |
| America/Chicago | Central Time | UTC-6 | UTC-5 |
| America/Denver | Mountain Time | UTC-7 | UTC-6 |
| America/Los_Angeles | Pacific Time | UTC-8 | UTC-7 |
| Europe/London | UK Time | UTC+0 | UTC+1 |
| Europe/Berlin | Central European | UTC+1 | UTC+2 |
| Asia/Tokyo | Japan Standard | UTC+9 | None |
| Australia/Sydney | Australian Eastern | UTC+10 | UTC+11 |
Daylight saving time edge cases
DST transitions create two tricky situations that a reliable time zone converter must handle. During the spring-forward gap, a local time such as 02:30 simply does not exist; clocks jump from 01:59 to 03:00. During the fall-back overlap, a time like 01:30 occurs twice: once before the transition and once after.
This tool resolves ambiguous times by using the first occurrence (the pre-transition offset) and says so in the result. Non-existent times are rejected with an error, so you can pick a valid time instead of getting a silently shifted answer.
Practical uses for a time zone calculator
Scheduling calls across continents is the most common reason people search for a time zone calculator. If you work in New York and need to call a colleague in Sydney, entering 09:00 on a Monday in America/New_York will show you that it is already late Monday night or early Tuesday morning in Australia/Sydney, depending on the time of year.
Other everyday uses include checking when a live broadcast airs in your city, confirming flight arrival times shown in local airport clocks, and coordinating software deployments across distributed teams. For planning meetings with three or more participants, consider a dedicated world time meeting planner.
IANA time zone identifiers
Rather than relying on ambiguous abbreviations like EST or CST, this converter uses IANA time zone identifiers such as America/New_York or Asia/Kolkata. Each identifier maps to a complete historical record of UTC offsets and DST rules for a specific region.
The identifiers follow an Area/Location pattern. The area is typically a continent or ocean, and the location is a major city that represents the rules for that zone. Using these identifiers avoids confusion: for instance, eastern time to central time conversions depend on knowing exactly which jurisdictions observe DST and when they transition.
Worked examples
| Example | Input | Result |
|---|---|---|
| New York noon to London (summer) | Date: 2025-07-15; Time: 12:00; From time zone: America/New_York; To time zone: Europe/London | Target local time: 17:00; Target date: 2025-07-15; Target offset: UTC+1; Source offset: UTC-4; Equivalent UTC: 16:00 (2025-07-15) |
| Tokyo morning to Los Angeles | Date: 2025-01-10; Time: 09:00; From time zone: Asia/Tokyo; To time zone: America/Los_Angeles | Target local time: 16:00; Target date: 2025-01-09; Target offset: UTC-8; Source offset: UTC+9; Equivalent UTC: 00:00 (2025-01-10) |
| Sydney evening to UTC | Date: 2025-12-25; Time: 20:30; From time zone: Australia/Sydney; To time zone: UTC | Target local time: 09:30; Target date: 2025-12-25; Target offset: UTC+0; Source offset: UTC+11; Equivalent UTC: 09:30 (2025-12-25) |
FAQ
Does this time zone converter account for daylight saving time?
Yes. It uses the IANA time zone database built into your browser, which contains the full history of DST rules for every supported zone. The correct offset is applied based on the exact date you enter.
Why use IANA zone names instead of abbreviations like EST or PST?
Abbreviations are ambiguous. EST could mean Eastern Standard Time in North America or Australian Eastern Standard Time. IANA identifiers like America/New_York point to one precise set of rules, eliminating confusion.
Can the converted time fall on a different calendar date?
Yes. When the offset difference is large enough, converting a late-evening time eastward or an early-morning time westward can shift the result to the next or previous day. The tool displays both the time and the resulting date.
Is my data sent to a server?
No. All conversions happen locally in your browser using the JavaScript Intl API. Nothing is uploaded anywhere.
What happens if I enter a time during a DST gap?
During the spring-forward transition some local times do not exist (for example 02:30 in New York on the second Sunday of March). The converter shows an error asking you to pick a different time rather than guessing.
How do I convert between US Eastern and Pacific time?
Select America/New_York as the source and America/Los_Angeles as the target. For a dedicated page, see the eastern to pacific time converter.